Control system for electric cooking ovens



7 Oct. 22, 1940. WEIMER CONTROL SYSTEM FOR ELECTRIC COOKING OVENS Filed Sept. 13, 1939 Patented Oct. 22, 1940 UNITED STATES PATENT OFFICE CONTROL SYSTEM FOR ELECTRIC COOKING OVENS Leland S. Weimer, Newark, Ohio Application September 13, 1939, Serial No. 294,620

4 Claims. (Cl. 219-20) This invention relates to a system of control for electric cooking ovens'of the type having a lower heating element and an upper heating element adapted to be selectively connected in cir- 5 cuit for meeting the requirements of bakej' pre-heat, and broil conditions.

In one old system now in use, in order to obtain .pre-heat conditions, both of the elements are connected across the outside lines of a threewire system so that 220 volts are impressed upon each of the elements, and, in order to obtain broil conditions, only the upper element is so connected. In order to obtain bake conditions, which require a high heat emanation from the lower element and a reduced rate from the upper element, the lower element is connected across the outside or live lines and the upper element, together with a resistor in series therewith, is connected across one outside line and the neutral wire. This old system has been found objectionable in that when the switch, through which the elements are selectively controlled, is operated from bake to pre-heat positions, or vice versa, the polarity of the contacts of the switch are reversed, objectionable arcing at the switch contacts results; and short circuiting sometimes occurs. The use of a resistor or rheostat is also objectionable in that it is an additional expense and results in the wasting of wattage.

in another system now in use, a baking element is located in the bottom of the oven, and a baking element of less capacity and also a broil element is located in the top of the oven, and the top baking element is somewhat shielded from 95 below. That arrangement is a more or less expensive one.

The aim of the present invention is to provide an improved and economical arrangement wherein the desired conditions for pre-heat,"

e0 broil, and bake are effectively established and maintained across the same two lines of the power source so that there is no switching from one voltage to another, which means that chang-,

50 The invention accordingly consists in the features of construction, combination of elements,

and arrangement of parts which will be exemplifled in the construction hereafter set forth and the scope of the application of which will be in- 55 dlfilted in the appended claims.

In the accompanying drawing, wherein is shown for illustrative purposes one embodimentwhich the present invention may take;

Figures 1, 2, and 3 are diagrammatic views illustrating the circuits of the system for provid- 5 ing conditions of bake, pre-heat, and broil, respectively.

Referring to the drawing in detail, A designates the oven of an electric range or the like; the same being shown in outline as the .particu- 10 lar construction thereof forms no part of the present invention. B designates a two-part heating element located in the bottom of the oven; the parts of this element being respectively designated by the numerals l0 and II. C desig- 15 nates the broil element located in the upper portion of the oven. The switch D for controlling the elements may be of any suitable type, the one shown in the drawing being for illustrative purposes only. The switch in the present 29 instance has a terminal contact l2 with which cooperates a pair of movable contacts l3 and M. The switch further has a pair of contacts I5 and I6 adapted to be moved into and out of engagement with one another. The contacts may be 25 carried by suitable switch arms or members ll. Suitable means, such as a switch handle or the like, is, of course, provided for selectively moving the switch arms. This means is not shown in the present instance as its form is immaterial to 3 the invention.

The terminal I2 is connected to one of the outside lines L of the power source by a wire 2|. The switch arm carrying the contact I3 is connected by a wire 22 to one end of the bake" element B. The other end oi this element is connected by a wire 23 to the other outside line L. A neutral or third wire N is shown in the drawing to indicate that if a three-wire circuit is utilized instead of a two-wire one, the third wire is not required. The arm carrying the contact I5 is connected to the element B between the parts H1 and II thereof by a wire 24. The arms which carry the contacts I4 and iii are connected to one end of the. broil unit C by a wire 25, and the other end of this element C is connected by a wire 26 and the wire 23' to the line L.

With the arrangement described, it will be understood that when it is desired to pro-heat the oven, both elements are connected through the outside lines, as illustrated in Figure 2, so that a 220 voltage (for. example) is impressed upon each unit, with the result that the oven is brought up quickly to the desired temperature. In this instance, the two contacts l3 and I4 engage the terminal l2, and the two contacts I 5 and I6 are separated from one another. When a broiling operation is required, the switch is moved to the position shown in Fig. 3, and in which position the contact M engages the tere minal l2, the other contacts being in open positio-ns so that the broil unit C is connected across the outside lines and the bake unit is out of circuit. When a baking condition is desired, the switch is moved to the position shown in Fig. 1, wherein the contact l3 engages the terminal l2, the contacts I and 16 are in engagement with one another, and the contact I4 is in open position.

It will be observed from Fig. 1 that when the switch is in the bake",position, the part II of the bake" element andthe broil" unit C are in parallel with each other and in series with the part ID. .The current flows from the line L through the engaged contacts 12 and 13, through the part H] of the bake element, and it then splits. part going through the part II and part going through the broilf unit, and thence the current flows through wires 23 and 26 to the other outside line L.

It is, of course, understood that by changing the tap point at which the wire 24, leading to the contact I5, is connected to the bake elernent B, the amount of current passing through the broil element during baking can be controlled by varying the size of the portion ll of the "bake element, B with respect to the broil element C.

It will be observed from the foregoing disclosures takenin connection with the accompanying drawing that in each operative position of th switch the element or elements in operation are connected across the same two supply lines, and in no instance is there a switch it is intended that all matter contained in the above description or shown in the accompanyranged to selectively connect ing drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebet'ween.

I claim as my invention:

1. In a control system for electric ovens, a pair of supply conductors, atwo-part baking element, a broil element, and switch means constructed and arranged to connect both of said elements in parallel across said conductors; the broil element only across said conductors; and one part of said bake element and said broil element in parallel and the other part of said bake element in series therewith across said supply conductors.

2. In a control system for electric ovens, a pair of supply conductors, a two-part baking element, a broil element, and switch means constructed and arranged when in one position to connect the 'bake element and the broil element in parallel across said lines to obtain pre-heat conditions within the oven, to connect in another position the broil element across the two said lines to obtain broil conditions, and, in a third or bake position, to connect both parts of the bake element across said lines in series, and said broil element between said parts and one of said linesfwhereby said broil element is in parallel with one part of said bake; element.

3. In a control system for electric ovens, a pair of supply conductors, a two-part baking element, abroil element, and switch means arid elements across said lines, in-pne position of said switch both partsof said bake elements being connected in series across said lines and said broil element being connected in parallel with only one part of said bake element. 7

4. In an electric circuit for an electric oven, a pair of supply lines, a multi-part heating element, a second heating element, and, means for selectively connecting said elements across said lines, in one position of said switch one part of said multi-part heating element being connected in parallel with said second element and another part of said multi-part element in series therewith.

LELAND S. WEIMER. 

